Mutant blue-eyed coyotes spreading through California

LAST SPRING, A photographer and guide in northern California’s Point Reyes National Seashore named Daniel Dietrich spotted an unusual animal: A female coyote with blue eyes. Blue is an incredibly rare eye colour for coyotes, and it’s likely caused by a chance mutation.

Now, it appears the trait is spreading. In the last few months, at least four other coyotes with blue peepers have been seen and photographed within about a 160-kilometre radius of the seashore.

Dietrich, who happened upon the original coyote one fine April morning, at first didn’t think she was anything special. She sports tall, lanky legs, a silvery-brown coat for camouflage, and large, triangular ears that help her listen for gophers hidden in the grass.

However, while almost all coyotes have golden-brown irises, hers are icy-blue. National Geographic investigated Dietrich’s find in June of 2018, calling the coyote potentially “one in a million.”

Since then, coyotes with baby blues have been seen and photographed to the east near Sacramento, and far to the south, outside Santa Cruz. Two are now known to live in Point Reyes—an eye injury to the first enabled photographer David Kramer to definitively identify the second.

Two blue-eyed coyotes, presumably siblings, forage in a field before dawn in Santa Cruz, California. The third coyote they accompanied, not pictured, had dark brown eyes.
PHOTOGRAPH BY CARTER KREMER

Blue streak

Due to the localised nature of the phenomenon, and the complete absence of it elsewhere in the country, scientists now hypothesise that a mutation to the genes that control eye colour likely appeared several generations ago, and these newly-documented canines are recent descendants of one original “one-in-a-million” mutant.

Coyotes tend to disperse from their natal grounds after a year or two in search of new territory, often travelling 10 to 20 miles or more through urban landscapes and crossing dangerous roads—even San Francisco’s Golden Gate Bridge. So a distance of 160 kilometres could be easily covered in a few generations.

While the occurrence of such a mutation is rare, the alternative—introduction of the gene through hybridisation with domestic dogs—is more unlikely in this case.

Coyotes and dogs can interbreed to form “coydogs.” These animals typically have significant changes in coat colour and altered facial structure and proportions, says Stan Gehrt, a wildlife ecologist at Ohio State University and a National Geographic explorer. But Gehrt has never seen a change in eye colour.

Golden-brown eyes have been selected for through millions of years of coyote evolution. “They have the colour which is best for their environments and their way of living,” says Juan Negro, a scientist with expertise in animal eye hue.

Thus, blue irises are almost certainly not advantageous to these animals, and it’s even possible that they could have downsides like interfering with camouflage or causing increased light sensitivity, Negro says.

In other animals, like dogs, blue eyes have been selected through artificial breeding. Wolves, for example, do not have blue irises.

In many ways, coyotes have it better now than in the past. Humans have killed or driven out many of their predators, such as wolves and mountain lions (and, even farther back, fierce carnivores like dire wolves and sabre-toothed cats). Thus, there are different—and more relaxed—selective pressures on the animals.

Without the presence of those apex predators, blue eyes are probably less likely to be selected out of the gene pool, Negro says. According to the photographers, all five observed blue-eyed coyotes appear to be healthy and hunting successfully, meaning the gene may be here to stay.

Understudied

For these striking ambassadors of a species whose ecological role in rodent and disease control is widely underappreciated, the greatest threats to survival seem to be the same as every other coyote: cars, hunters, and the U.S. government.

An estimated 500,000 coyotes per year are killed throughout North America, with approximately 80,000 of that number falling victim to the lethal control methods—including aerial gunning—carried out by Federal officials on taxpayer dollars. In spite of these control efforts, coyotes persist.

And they remain grossly understudied, says Camilla Fox, the founder and executive director of the local nonprofit Project Coyote.

By better understanding coyotes, she says, which are the only canine solely found in North America, “I think we can learn a lot about adaptability and resilience… in the face of ecological and social upheaval.”

Until researchers are able to study these majestic mutants through scientific means—by collaring them to track their movements and analysing their DNA—local photographers will continue to piece the story together, one frame at a time.